Import patches-unapplied version 2.4.18-2ubuntu2 to ubuntu/xenial-proposed

Imported using git-ubuntu import.

Changelog parent: 00d5abc3c62fc321395832bde92c84c9ef93096f

New changelog entries:
* Correct systemd-sysv-generator behavior by customizing some parameters (LP: #1488962)
- d/apache2-systemd.conf: add a drop-in file to specify some parameters for the systemd
unit (type=Forking and RemainsAfterExit=no), this allow a correct state synchronisation
between systemctl status and actual state of apache2 daemon.
- d/apache2.install: place the apache2-systemd.conf file in the correct location.